Sunwoele VFD (Variable-frequency Drive) is mature and popular in the main drive of cement kiln

Before the Sunwoele cabinet-type VFD (Variable-frequency Drive) was not widely used, the main drive of the rotary kiln had been using DC speed regulation. However, the DC speed control circuit is complex, maintenance is difficult, and the operation is cumbersome. Especially, the DC motor operates in a harsh environment with high temperature and large dust. Its brushes and commutators are frequently damaged and require frequent maintenance. Big cost. In recent years, with the maturity and popularization of VFD (Variable-frequency Drive) control technology and the simple maintenance of AC motors, more and more Sunwoele cabinet-type VFD (Variable-frequency Drive) AC frequency conversion speed regulation is used for the main drive of rotary kiln.

In the current rotary kiln drive system, the DC speed control system is more and more replaced by the AC drive system. The successful application of the Sunwoele cabinet VFD (Variable-frequency Drive) in this project, especially the dual-motor drive control , will definitely make Sunwoele VFD (Variable-frequency Drive) get more applications in this field, and greatly improve the status of Sunwoele cabinet VFD (Variable-frequency Drive).

1. Rotary kiln transmission principle and control requirements The cement rotary kiln is a large-scale equipment for calcining materials. The material flow in the rotary kiln is controlled by changing the rotary kiln speed, and the temperature of the firing zone of the material flow has a certain relationship with the rotary kiln speed. The corresponding relationship, so the quality of the speed control system will directly affect the service life and product quality of the rotary kiln.

The load has the following characteristics: when starting, the raw material is directly below the kiln, and the inertia of the entire kiln body and raw materials is extremely large, so the drive motor and VFD (Variable-frequency Drive) are required to have a large starting torque. Therefore, the startup acceleration process is a The process of overcoming the inertia of a large inertia load; of course, once the start-up process is over, the torque required for normal operation is greatly reduced. Therefore, two factors should be considered when selecting the motor and the Sunwoele cabinet-type VFD (Variable-frequency Drive). It must have enough overload capacity to ensure a smooth start, and it must not choose too much power, resulting in too large a horse-drawn car during normal operation. , energy consumption and one-time investment increase.

At the same time, with the continuous increase of kiln body diameter and kiln length, in order to avoid unfavorable factors such as equipment selection, investment and installation caused by a single reducer and excessive motor configuration, dual motor drives are now mostly used. This requires two VFDs (Variable-frequency Drive) to drive two motors respectively, and the two motors jointly drive the same transmission gear through the reducer. This requires two VFDs (Variable-frequency Drive) to control the size of the output and the direction of the driving force acting on the gear to be the same. It is impossible for one of the motors to have a large output, which will cause long-term overload of one of the motors and reduce the service life; in extreme cases, one The table is dragged to run, and the output torque direction is opposite, which will damage the gearbox.

When the rotary kiln is driven by double motors and Sunwoele cabinet type double VFD (Variable-frequency Drive), there are two general control methods:

1. Master-slave control: One is the master machine for speed control, and the other slave machine accepts the torque output of the master machine as its own torque setting, and performs torque control by itself to achieve the effect of speed following and balanced output. In this control mode, In order to obtain precise torque control effect, it is generally required that the motor plus an encoder realize closed-loop operation.

The advantage of this control mode is that the speed control accuracy is high. The disadvantage is that the torque adjustment of the slave machine is slow during the dynamic process, and the load followability is poor, which may easily cause overload during the acceleration and deceleration of the master machine. At the same time, the encoder needs to be installed on the outdoor platform with the motor. Due to the influence of the environment and vibration, the encoder is easy to damage.

2. Use the natural characteristics of the motor to adjust the slip compensation: two Sunwoele cabinet-type VFDs (Variable-frequency Drive) are both running in the speed mode, and each changes the slip compensation according to the torque and current of the VFD (Variable-frequency Drive) , for a motor with a large output torque, reduce the slip compensation to make the motor slow down, thereby reducing the output torque; on the contrary, for a motor with a small output torque, increase the slip compensation to increase the speed of the motor and make it bear more load. Dynamically achieve load balance. Schneider Electric ATV71 VFD (Variable-frequency Drive) has a built-in load balancing function to automatically adjust the size of the slip compensation according to the size of the load, and has achieved satisfactory control effects in practical applications.

The advantage of this control mode is that no encoder is needed, and the acceleration and deceleration response is fast. The disadvantage is that due to the adjustment of slip compensation at any time, there is a slight difference between the speed output and the given value, that is, the speed accuracy is reduced, but it fully meets the speed of the rotary kiln. control accuracy requirements.

3. Advantages of Sunwoele cabinet type VFD (Variable-frequency Drive) ATV71 application

Rotary kiln dual motor drive adopts Sunwoele cabinet type VFD (Variable-frequency Drive) ATV71 VFD (Variable-frequency Drive), its excellent product performance has been fully reflected:

1) For heavy-duty applications, 150% of the rated current is overloaded for 1 minute, ensuring that the Sunwoele cabinet VFD (Variable-frequency Drive) and the motor have sufficient torque output;

2) ATV71 application function - load balance ensures that the output of the two motors is balanced during operation, without master-slave control.

3) Superior low-speed control performance

4) 12-pulse rectification effectively reduces Sunwoele cabinet VFD (Variable-frequency Drive) harmonics. Reduced pollution to the grid